In several communications systems the data to be transmitted is compressed so that the available bandwidth is used more efficiently. For example, the Moving Pictures Experts Group (MPEG) has promulgated several standards relating to digital data delivery systems. The first, known as MPEG-1 refers to ISO/IEC standards 11172 and is incorporated herein by reference. The second, known as MPEG-2, refers to ISO/IEC standards 13818 and is incorporated herein by reference. A compressed digital video system is described in the Advanced Television Systems Committee (ATSC) digital television standard document A/53, and is incorporated herein by reference.
The above-referenced standards describe data processing and manipulation techniques that are well suited to the compression and delivery of video, audio and other information using fixed or variable length data structures within digital communications systems. In particular, the above-referenced standards, and other xe2x80x9cMPEG-likexe2x80x9d standards and techniques, compress, illustratively, video information using intra-frame coding techniques (such as run-length coding, Huffman coding and the like) and inter-frame coding techniques (such as forward and backward predictive coding, motion compensation and the like). Specifically, in the case of video processing systems, MPEG and MPEG-like video processing systems are characterized by prediction-based compression encoding of video frames with or without intra- and/or inter-frame motion compensation encoding.
When encoding video information it is seen to be desirable to adapt the encoding process to video source formatting parameters and encoded video formatting parameters. Unfortunately, such adaptation of the video encoding process tends to be extremely expensive in terms of both processing power and memory requirements. As such, designers of video encoders typically utilize approximations of various parameters to ease computational and memory overhead to a xe2x80x9creasonablexe2x80x9d level, as defined by a particular application (e.g., professional use or consumer use).
Therefore, it is seen to be desirable to address the above-described problems by providing a robust and computationally efficient method and apparatus for adapting and/or enhancing the behavior of a video encoding process to video source formatting parameters and encoded video formatting parameters. Specifically, it is seen to be desirable to provide a video encoding method and apparatus, such as an MPEG-2 video encoding method and apparatus, that provides relatively low computational complexity and reduced memory bandwidth requirements, along with graceful and robust video quality scalability across a wide range of encoding bitrates.
The invention comprises a method and apparatus for encoding, illustratively, a video information stream to produce an encoded information stream according to a group of frames (GOF) information structure. In various embodiments of the invention, modifications are made to the GOF structure and a bit budget in response to, respectively, information discontinuities and the presence of redundant information in the video information stream (due to, e.g., 3:2 pull-down processing). Additional embodiments of the invention efficiently utilize pyramid processing techniques, packed data representations and other methods to achieve highly efficient utilization of memory and/or processing resources within the encoding environment.
Specifically, an encoding system according to the invention comprises: an encoder, for encoding each of a plurality of pre-processed information frames substantially in accordance with a group of frames (GOF) information structure; a controller, for adapting the GOF information structure in response to an inter-frame information discontinuity within the plurality of information frames; and a pre-processor, for receiving and processing a plurality of information frames to produce the plurality of pre-processed information frames, the pre-processor identifying and generating an indicium of the inter-frame information discontinuity within the plurality of information frames.